[Lynn Eades]

Hanno the modern grease is not going to move, where as the oil might. I would put mine in to keep the oil out. (i have said already that the need for a seal at all, is dependant on how steep the sidings are that you might run / park on.
As the carrier is very likely to throw a track sidling a hill, I would be inclined to not worry too much about which way it is fitted. It is recommended to a ascend or decend hills directly, rather than sidling
I believe it was made to keep the oil out(of the wheel bearings) and limited to the diff and axle tube.
Paul, me and my photos are in another country, from my carriers ( a bit like you being in Poland) so can't help with the physical stuff.
Phill, sorry, I can't help.